Pressure indicator

Abstract

The pressure indicator has a body provided with an attachment shank having a pressure fluid passage. A cylinder bore is located at one end of the body communicating with the passage and has a threaded open end. An end plug having a bore and a counterbore is snugly threaded into the open end. A piston is nested in the cylinder bore and has a piston rod axially extending through the cylinder bore and projecting through and outwardly of the plug. A compression spring is interposed between the plug and piston and yieldably biases the piston towards said one end of the cylinder bore. The piston is variably movable longitudinally against the spring on application of pressure to the shank passage. A bearing or bushing is nested within the plug bore and axially and guidably receives the piston rod. The improvement resides in the bushing or bearing having a depending tapered boss of reduced diameter with an annular inclined surface extending downwardly and inwardly at an acute angle, therebeing a counterbore in the bushing and axially of the boss. A cylindrical slide seal of plastic material is nested within the plug bore and projects into the counterbore and boss and depends from the bushing in sealing engagement with the piston rod. An O-ring in the plug bore is sealingly interposed between the plug and the slide seal and in compressed operative registry with the boss and in operative retaining registry with the seal.

I claim: 
     
       1. In a pressure indicator having a body with an attachment shank with a pressure fluid passage, a cylinder bore at one end communicating with said passage and having a threaded open end, an end plug having a bore and a counterbore snugly threaded into said open end, a piston nested in said cylinder bore having a piston rod axially extending through said cylinder bore and projecting through and outwardly of said plug, and a compression spring interposed at its ends between said plug and piston yieldably retaining said piston at one end of said cylinder bore, said piston being variably movable longtudinally against said spring on application of pressure to said shank passage, the improvement comprising; a bushing nested within said plug bore having a bore axially and guidably receiving said piston rod and counterbore;   an annular tapered boss of reduced diameter on and depending from said bushing with its outer surface inclined downwardly and inwardly at an acute angle with respect to the axis of said bushing;   said bushing counterbore extending axially through said boss;   a cylindrical slide seal of plastic material within said plug bore and snugly producted into said boss and bushing counterbore and depending from said boss in sealing engagement with said piston rod within said bushing and boss, and below said boss; and   an O-ring in said plug bore sealingly interposed between said plug and slide seal and in operative compressive engagement with the angular surface of said boss;   said angular boss surface providing for increased operative sealing and pressure engagement of said O-ring between said plug and seal.   
     
     
       2. In the pressure indicator of claim 1, said piston rod being of a material different from said bushing thereby eliminating binding therebetween. 
     
     
       3. In the pressure indicator of claim 1, said piston rod being of stainless steel. 
     
     
       4. In the pressure indicator of claim 1, said piston rod having a highly polished microfinish. 
     
     
       5. In the pressure indicator of claim 1, a nickel-plated layer applied to said piston rod. 
     
     
       6. In the pressure indicator of claim 1, said body longitudinally inward of said shoulder having an annular tapered surface spaced from said plug below said top flange; and an O-ring seal compressively nested between said tapered surface and plug.   
     
     
       7. In the pressure indicator of claim 1, the acute angle of the tapered surface of said bushing boss being 50 degrees approximately. 
     
     
       8. In the pressure indicator of claim 1, the acute angle of the tapered surface of said bushing boss being in the range of 40 to 60 degrees approximately. 
     
     
       9. In the pressure indicator of claim 1, said body outwardly of its threaded end having a counterbore of increased diameter defining a stop shoulder; a transverse top flange on said end plug nest in the counterbore of said body and bearing against said shoulder;   end portions of said body at said counterbore being inturned limiting relative outward movement of said top flange relative to said body, whereby application of an over-pressure to said plug is relieved over a controlled orifice area providing a safety relief.